var iframe = document.querySelector('#iframe')
var arr = ['./page/zhuanye.html','./page/xuey.html', './page/fangpc.html']
var span = document.getElementsByTagName('span')
// console.log(span)
span[0].setAttribute('class','active')
function clic(i){
    iframe.src=arr[i]
    for(var s = 0;s<span.length; s++){
        span[s].removeAttribute('class','active')
    }
    span[i].setAttribute('class','active')
}